Climate Change and Tetrapod Evolution

Question 1

What is climate?

Answer 1

weather statistics over a long period of time

(weather = measured over days, months, + seasons)

Question 2

Sources of information about past climate?

Answer 2

• sedimentary rock - presence/absence of water, marine life, sedimentary deposits, isotope ratios, Mg/Ca ratios
• ice cores in Greenland go back 800k years now. Air trapped in frozen bubbles. Layering, oxygen isotopes indicate ocean surface temp, pollen, volcanic ash. Oldest cores will go back to 1.5 Ma
• Tree rings dendrochronology - back 500yrs with tree rings
• Coral sclerochronology - chemical variation in hard tissues
• landforms

Question 3

Global temperature during tetrapod evolution

Answer 3

• tetrapods emerge from sea when planet was warm
• rapid global cooling led to Carboniferous rainforest collapse - extinction of many amphibians and evolution and diversification of amniotes
• Cooling climate and expansion of grasslands in Cenozoic correlates w/ increasing mammalian body size
• Fleistocene extinction of megafauna
• mostly stable 30-40yrs ago - now warming quickly

Question 4

Transitions between land and water (looking ahead)

Answer 4

warming climate and increased competition on land leading to marine transgressions?

warm climate = less land and more sea

cooling climate and increased marine productivity?

Question 5

Drivers of tetrapod decline?

Answer 5

• habitat loss
• over-exploitation
• biological invasions
• pollution
• climate change

Question 6

Strategies to investigate what life will be like following climate change?

Answer 6

• investigate evolutionary responses to extreme weather events
• longitudinal studies
• Paleontological studies

Question 7

Strategy: Extreme Events
How does climate warming affect extreme events?

Answer 7

climate warming increases frequency of extreme events

Question 8

Can species adapt fast enough to current rates of climate change?

Answer 8

weather events the rate of change = extreme

rapid environmental changes stress populations

More gradual global warming in last 50 yrs can be seen through longitudinal studies

Question 9

Longitudinal studies

Answer 9

Long-term field studies are the best way of learning about contemporary climate change

little evidence of species evolving increased thermal tolerance

most changes linked to climate change are in phenology - the timing of key events in an organisms life

Question 10

Longitudinal study - Phenology - Great tit laying date

Answer 10

variation in great tit population laying date

warming climate hatching lepidopteran (insect) eggs earlier

tits that lay earlier have higher fitness as there are more caterpillars to feed their young

Early-bird offspring go on to produce more offspring than late bird offspring

Question 11

Longitudinal Studies - Morphology - Bergmann’s rule

Answer 11

• Bergmann’s rule: body size increases at high latitudes / low temperatures - Sand et al. (1995)

Question 12

morphological adaptations to climate change

Answer 12

• difficult to show, only few studies have done so for terrestrial vertebrates
• common garden and experimental evolution designs do not work for large, long-lived animals

Question 13

Can species adapt fast enough to current rates of climate change?

Answer 13

• range shifts are not an option for many populations, or may only provide a partial solution
• plasticity & learning are insufficient in the long-term as changes are not inherited
• this leaves genetic changes, where the rate of adaptation is primarily set by the rate of microevolution
• most studies, so far, have shown animals responding to climate change by utilising phenotypic plasticity (phenological/morphological)
• limited evidence for evolutionary response to climate change thus far, but a few studies are showing that it is happening
• whether the rate of microevolution can be fast enough is unanswered - longitudinal genomic studies?